Mayor de Blasio on Tuesday would not commit to banning contributions from people who do business with the city when he launches a legal defense fund to deal with multiple investigations.

He also wouldn’t say whether he’ll take Comptroller Scott Stringer’s advice and seek guidance from the city’s Conflicts of Interest Board on the proper structure of the fund.

“We will set up a clear standard that is fair and avoids a conflict, but I am not going to go into details because that will take a lot of work and a lot of hours to figure out what is the right way to do things,” he told reporters at an unrelated press conference in Manhattan.

The mayor has also said he has yet to pay a single bill to his lawyer, Barry Berke at Kramer Levin, even though he was retained in April.

Republican mayoral candidate Paul Massey has seized on that arrangement in calling for an investigation — and he hit de Blasio again Tuesday at a press conference outside City Hall.

“Bill de Blasio is corrupt and New Yorkers deserve to know how deep the rot is at City Hall,” said Massey, a real estate executive. “It’s not a rumor or an accusation, it’s a fact.”

The mayor has insisted that he followed legal guidance in all of his fundraising efforts, which are under investigating by the US Attorney and the Manhattan DA.

At one of his first press conferences, Massey wasn’t able to provide any details of his own plans for tackling issues like homelessness or NYPD reform.

Asked whether he supports increasing or decreasing the policing tactic known as stop and frisk, Massey said, “I haven’t established an answer.”

That response drew a jab from de Blasio — who joked that “the issue has not been in the news the last few years, so who can blame him?”